In the race to dominate the fast-growing digital health industry, Google unveiled a service Wednesday that collects users' fitness data in one place.

The service, Google Fit, was one of many announcements at the Mountain View company's annual developer conference in San Francisco. Just weeks before, Apple and Samsung Electronics had revealed their plans to capture consumers' health information.

Google Fit will aggregate data from popular fitness trackers and health apps. It will do so by working with Nike, Adidas and other companies whose wearable devices will sync to the platform. In the next few weeks, Google will hand out open APIs - instructions that allow apps to share information - so developers can make apps that manage multiple types of data.

"We want to help users keep better track of their fitness goals," Ellie Powers, product manager for Google Play, told a packed room at Moscone Center. "Before Google Fit, I was trying to track and monitor my bike rides through a bike computer, and my weight training through specialized apps, and it was a huge hassle. The information was way too siloed to actually help me."

Not everyone was impressed.

"I didn't see much ambition here," said Malay Gandhi, managing director of Rock Health, a San Francisco accelerator that funds digital health startups. "I saw something that looked very much like other data-aggregation platforms for consumer apps and devices. I didn't see anything that moved it past where we already are today."

The real, unaddressed challenge, Gandhi said, is to get data into the hands of doctors and hospitals, so biometrics can be turned into meaningful advice.

As health information grows more digitized and people increasingly want control over it, Google is the latest to try to make itself the leader in the industry. It's too early to tell who will come out ahead, Gandhi said, but it "doesn't necessarily have to be winner take all."

This month Apple unveiled Health, an app that allows users to collect biometrics such as monitoring heart rate, calories burned and blood sugar, and automatically send data to doctors or hospitals.

The Cupertino company announced Health in partnership with Epic Systems, one of country's largest suppliers of electronic medical records systems, and the Mayo Clinic in Minnesota. The implication, analysts say, is that users will have much greater access to, and the ability to share, their information in the not-so-distant future.

In May, Samsung introduced the Simband, a prototype for a smart watch that can track users' vital signs and connects to a cloud platform.

On Wednesday, Google introduced its version. Its Android Wear software powers two smart watches now on the market - Samsung Gear Live and LG G Watch - and the Moto 360, which will be available this summer. The gadgets, which can track users' steps and heart rate, may portend even more ambitious, sensor-tracking watches to come, analysts say.

Google has tried branching out into health before. In 2008, it introduced Google Health, an online dashboard where users could input and access their health records. Five years later, it pulled the plug on the service after it failed to attract users.

"We've now seen and we have proof that patients and consumers won't add their own clinical medical data to things manually," said Matt Douglass, co-founder and vice president of platform at Practice Fusion, a free electronic health record website in San Francisco. "But if we can aid automated data collection via devices people are already wearing or are carrying in their pockets, it lays the framework for a really big transformation in digital health."

Google has also been stepping into health in other ways. In September, it began a biotechnology company devoted to slowing down the aging process. In January, it said it was testing a "smart" contact lens intended to help diabetics by measuring blood sugar levels. And Google Glass is in partnerships with startups, such as Augmedix, that use Glass in clinical settings. None of those projects was mentioned Wednesday.